Monthly Archives: February 2013

Prisoner of Speed

A favourite podcast of mine is known in our household as “Danny’s podcast” in honour of the friend who first put me on to it. The podcast is better known as Radiolab and last week’s episode turned on the theme of Speed. After answering the question, what is the fastest sense, attention turned to high-frequency trading. As the Radiolab hosts are more comfortable with science than finance, they turned for assistance to David Kestenbaum from the Planet Money podcast.

In a past Mule post, I expressed reservations about the merits of high-frequency trading. Just last year, there was talk in the European parliament of enforcing a delay on electronic trading. Some critics argue that high-frequency trading creates instability in financial markets and may have been to blame for the “flash crash” of 2010.

One of the more intriguing aspects of high-frequency trading was brought out in the podcast during an interview with a technologist from the US trading firm Tradeworx. Bemoaning the cost of constantly competing to allow faster and faster trading (millions of dollars are being thrown at shaving milliseconds from the time to send trades to an exchange), he said that high-frequency traders were caught in a prisoner’s dilemma.

The prisoner’s dilemma is a staple of the study of the branch of mathematics known as “game theory“, which seeks to analyse strategic decision-making. Here is a quick overview for anyone unfamiliar with it.

Two criminals are arrested and taken to separate cells to ensure they cannot communicate with one another. The police have enough evidence to send each man to jail for one year. With a confession the police could get a conviction on a more serious charge. So, the police point out to each prisoner that cooperation will help reduce their sentence. If neither prisoner confesses, both will face one year in prison. If one testifies against his partner in crime, he will go free while the partner will get three years in prison on the main charge. But, if they both confess, that cooperation is not worth as much and both will be sentenced to two years in jail.

So, what should each prisoner do? No matter what the other prisoner does, confessing will improve their outcome, either from one year to none if the other does not confess, or from three years to two if the other does confess. So, the only rational thing to do is to confess. If both prisoners follow this logic, they will both get two years. And yet, if they had both kept quiet, it would have only been one year each, which would be better for both of them. The problem is that the “global optimum” is hard to obtain because there is too much of a risk for each prisoner that the other will defect.

The same is true for the high-frequency traders. While it might be cheaper for all of them to call a truce and freeze their technology at its current state, there would always be the risk that one firm breaks the truce and gains an edge. So, they all continue to compete in the speed race.

But the prisoner’s dilemma applies to more players than just the trading firms themselves.

If one of the major exchanges, such as the NASDAQ tried to stop the speed race, then it may well find itself losing business to any other exchange which continued to facilitate faster trading. An exchange without trading does not last long.

Governments too face the dilemma. There is already intense competition between exchanges operating in different countries and no government would want to lose the kudos and, more importantly, revenue that comes with playing host to a major financial centre. Would the UK government, for example, want to put London at a disadvantage to Europe or the US? Unlikely.

The German government is now delaying plans to curb high-frequency trading, in order to “clarify technical details”. I suspect that this will turn out to be a rather long delay.